Treatment of petroleum distillates



Patented May 11, 1937 umrao STATES PATENT ()FFICE TREATMENT OF PETROLEUM DISTILLATES George Hugo von Fuchs, Wood River, 111., and" Lawson Elwood Border, Boulder, C010.

No Drawing. Application November 13, 1931,

' Serial No. 574,920

d-"Qlaims. (01. 196-24) This invention relates to improvements in the treatment of petroleum distillates, and more particularly to an improved process of sweetening and rosion tests, and a low gum content, as well as an improved color stability and anti-knock value.

The specific objects of the invention will be sufficiently apparent from the following disclosure:

It is generally known that .many petroleum distillates of the general class referred to contain sulphur compounds such-as mercaptans, which cause such oils to have an unpleasant odor, a positive doctor test, a high sulphur content and corrosive properties, as well as a lack of color stability.

It is understood that the commonly used doctor treatment, employing sodium plumbite and free sulphur to convert the mercaptans to disulphides, does not reduce the sulphur content of the treated oils and, furthermore, that the treated oils have at times corrosive characteristics. It is also'recognized that the doctor treatment of oils produces a product that has relatively poor color stability, relatively high gum forming characteristic and,

furthermore, that the anti-knock rating of the doctor treated oils is lowered to a considerable degree and, in some cases, the sulphur content it concerned.

The present invention supplies a means of obviating the difficulties and deficiencies of the known sweetening and desulphurizing treatments and, therefore, produces a highly improved 40 product.

Broadly, the method of procedure includes the conversion of the mercaptans in the petroleum distillates, of the class above referred to, to copper mercaptides. The copper mercaptides are then 45 removed from the treated stock.

In order to effect the conversion of the mercaptans to the copper mercaptides various chemical means may be employed.

The distillate containing the mercaptans may be treated with different forms of metallic copper, as well as with copper oxides, copper chlorides, or other similar copper compounds. The reaction may be carried out with or without accelerators, depending upon the form of copper employed, the

55 type of distillate, the concentration and kind of mercaptans present, and whether or not the process is conducted as a continuous or batch operation.

The reactions between copper compounds and mercaptans are broadly of two types, depending upon whether a cuprous or a cupric compound is used. For example, cuprous oxide reacts with the mercaptans according to the following reaction:

The followingreactlons are suggested in the case of cupric oxide and are illustrative of other cupric compound reactions:

The step of the process whereby the mercaptans are converted to the copper mercaptides may be carried out at atmospheric temperature, and without the application of external heat.

When metallic copper is used in the conversion step it is preferably used in a form to provide an extended reacting surface such, for example, as turnings, filings, or powder. The copper may be supplied to the distillate under treatment as precipitated copper which, for example, may be obtained by adding metallic iron to a solution of a copper salt.

The copper, or copper compounds, may be used either in the 'dry state or in the form of a solution or suspension.

Under certain circumstances, it has been found that the reaction may be accelerated by the use of selected accelerators. Ammonia gas, hydrochloric acid gas, and sulphurdioxide gas dissolved t in the oil under treatment have been found to increase the rapidity of the reaction, although it is unnecessary to use an accelerator when the mercaptides are formed by the use of precipitated copper. The sulphur dioxide may originate from 40 a previous acid treatment. The accelerators indicated have been found to give a satisfactory accelerating action; although, in general, any oil soluble material of a basic or acidic nature, which has no harmful effect on the oil and which can be removed with suflicient ease after treatment, may be used 'as an accelerator. The effect of the accelerator seems to be that of an intermediate formation of a copper compound capable of more rapidly converting the mercaptans to copper 5o mercaptides than the original copper or copper compounds.

It has been found that the copper mercaptldes, formed by treating petroleum distillates with copper or copper compounds, are quite stable.

They do not hydrolyze or decompose as readily as do the lead mercaptides formed by the usual doctor treatment. They react very slowly with sulphur and, apparently, are not oxidized by an alkaline hypochlorite solution. They are much more readily removed from the distillate than the lead mercaptides.

The copper mercaptides formed in the oil undergoing treatment may be removed by various means, depending upon the type and the concentration of the mercaptides present.

For example, gasoline containing copper mercaptides may be distilled at a temperature up to 350 F. without turning sour. The gasoline may also be steam distilled in glass, copper or corrosion-resisting steel stills without hydrolysis. The distillation of the oil that has been treated to form the copper mercaptides causes appreciable reduction in sulphur content, since part of the copper mercaptides do not go overhead in the distillation but remain in the residue. The sulphur compounds going overhead are foundto be negative to the doctor test and are easily removed by acid treatment.

Mercaptans of the type present in cracked distillates when treated to form copper mercaptides yield copper mercaptides which are easily removed by sulphuric acid of such concentrations as are commonly used for treating such oils.

It has been found that copper mercaptides formed in straight run distillates often require concentrated or fuming sulphuric acid for removal.

It has been found also that ferric chloride is an effective reagent for the removal of the copper mercaptides. Since ferric chloride is soluble in hydrocarbons, it may be used in anhydrous as well as hydrated form and in water solution. Ap-

parently the eifect of the ferric chloride is twofold. It coagulates and precipitates part of the copper mercaptides, causing a corresponding decrease in the sulphur content of the distillate. The remaining mercaptides are then oxidized to disulphides. The first reaction is of importance only when ferric chloride is used in anhydrous or in hydrated crystalline form. In this case the treated distillate may show considerable reduction in sulphur content.

When concentrated solutions of ferric chloride are used, the copper mercaptides are completely converted to disulphides and copper chloride.

The following will illustrate thereaction:

The velocity of the reaction depends upon the concentration of the ferric chloride solution decreasing with decreasing strength. Below a certain concentration the hydrochloric acid, formed by the hydrolysis of the ferric chloride, tends to decompose part of the copper mercaptides and a sweet distillate cannot be obtained. It has been found, however, that if to the ferric chloride solution, before use in the treated oil, precipitated copper or certain cuprous compounds, such for example as copper oxide or copper chloride, are

with the mereaptans to form copper mercaptides.

The following will illustrate the reaction:

These mercaptides, immediately upon formation, are converted by the ferric chloride solution to disulphides, in accordance with the following reaction:

The ferric chloride in the treating solution can be replaced by ferric oxide and hydrochloric acid.

The spent ferric chloride solution, partly reduced to ferrous chloride, and containing the copper chloride can be revivified by oxidation with air. Therefore, with a given amount of ferric chloride and copper, an unlimited amount of distillate can be sweetened, provided the treating solution is properly revivified.

The copper may be recovered, if desired, from the treating solution in the form of a metallic precipitate by means of steel wool, iron filings, scrap iron, or the like.

A further method of sweetening sour distillates consists of mixing finely divided, that is to say precipitated copper, or copper compounds with clay, and passing through this mixture a sour gasoline containing an accelerator, such as ammonia gas. This particular method of treating is well adapted for treatment of sour cracked gasoline.

After the oils have been treated a redistillation with steam or steam and vacuum provides a method whereby the distillates are further improved, giving a final product of negligible sulphur and gum content and of high color stability.

As illustrative of the application of the process of the present invention, the following methods of procedure are suggested:

Sour cracked distillate may be first acid treated, then passed through copper turnings, then given the main acid treatment, then neutralized with caustic soda or with gaseous ammonia, and then steam-distilled to the required end point.

Sour cracked distillate containing ammonia gas may be first contacted with powdered copper, cuprous oxide or cupric oxide and the excess copper settled out or filtered. The distillate may then be acid treated with an amount and strength of acid normally required for treating similar sour distillates, and the then treated oil neutralized and steam distilled.

Sour cracked distillate may be contacted with precipitated copper, the excess copper separated by settling or filtering, the oil may then be acid treated according to known methods and then distilled with steam.

Sour cracked asoline containing dissolved ammonia'may be filtered through clay admixed with precipitated copper, cuprous oxide or cupric oxide, and the gasoline then water washed.

Sour straight run gasoline may be first acid treated, then without neutralization passed through fine copper turnings, then given a sec- 0nd acid treatment preferably of 100% strength, and then neutralized.

Sour straight run gasoline may be acid treated, then neutralized with ammonia, then contacted with cupric oxide and given a second acid treatment with sulphuric acid of 100% strength.

Sour cracked gasolines containing an accelerator, such as ammonia gas in solution, may be contacted with copper turnings or powder of copper or copper oxides and then passed through clay.

Sour straight run or cracked gasoline, naphtha or kerosene containing an accelerator, such as ammonia gas, may be passed through a mixture of clay and precipitated copper or copper powder or copper oxides and then water washed.

Sour straight run gasoline containing an accelerator, such as hydrochloric acid gas, may be passed over copper turnings and then treated with anhydrous or hydrated crystalline ferric chloride and then preferably filtered with vor through clay.

Sour straight run gasoline, containing dissolved hydrochloric acid gas, may be contacted with copper powder, cuprous oxide or cupric oxide, treated with concentrated ferric chloride, and then acid treated.

Sour straight run gasoline, naphtha, kerosene, or furnace oil, containing ammonia, may be contacted with powdered copper, or copper oxide, treated with/the concentrated ferric chloride solution, and'then acid treated.

Sour straight rungasoline may be contacted with precipitated copper, treated with concentrated ferric chloride solution, and then acid treated.

Sour straight run gasoline may be treated with a dilute solution of ferric chloride containing precipitated copper, copper oxide, cuprous chloride or like copper compound, then washed with water or dilute sulphuric acid solution, and then or furnace oil may be treated with a dilute solution of ferric chloride containing precipitated copper, and then acid treated.

The above illustrations of procedure will indicatethe wide range of the application of the invention. It should be understood, however, that the illustrations are merely by way of examples and that the invention is not limited thereto.

What we claim and desire to secure by Letters Patent is:-

1. In the process of refining a liquid hydrocarbon solution of mercaptans the step of treating the solution with an active copper reagent in the presence of aneifective quantity of extraneous gaseous ammonia.

2. In the process of refining a liquid hydrocarbon solution of mercaptans, the step of treating the solution under non-cracking conditions with an active copper reagent and ferric chloride in the presence of an effective quantity of extraneous gaseous ammonia.

3. In the process of refining a liquid hydrocarbon solution of mercaptans, the steps of treating the solution with metallic copper in the presence of an efiective quantity of added gaseous ammonia.

4. In the process of refining a liquid hydrocarbon solution of mercaptans, the steps of treat: ing the solution with a mixture of an active copper reagent and a refining clay in the presence of an effective quantity of added gaseous ammonia.

5. In the process of refining a liquid hydrocarbon solution of mercaptans, the steps of diSSOlV-r ing in the solution an effective quantity of ammonia and then treating the resulting solution with an active copper reagent to convert said dissolved mercaptans to copper mercaptides.

6. In the process of sweetening a liquid hydrocarbon solution of mercaptans, the steps of treating the solution with an active copper reagent in the presence of an effective quantity of added gaseous ammonia to convert said mercaptans to copper mercaptides, and separating the hydrocarbon liquid from the mercaptldes.

GEORGE HUGO von FUCHS. LAWSON ELWOOD BORDER. 

